This invention relates to a transfer trip system for controlling the operation of a remotely located circuit breaker in response to the operation of a local circuit breaker, and more specifically relates to a transfer trip system in which an annunciator at the remote station can be operated only when the pilot wire connecting the two stations has developed a fault, without causing the operation of the remote circuit breaker.
Transfer trip systems are well known wherein a remote circuit breaker is tripped in response to the tripping of a local circuit breaker. Typically, the circuit breakers are operated by respective relaying systems which are connected to one another by a pair of pilot wires, which could, for example, be two miles long. A d-c source is provided for the transfer tripping operation, and an a-c source is provided to monitor the pilot wires for short circuits and open circuits. Complex relay schemes have been required to integrate the two sources. There is also the possibility that false tripping could be caused by transients in the pilot wires, especially when the pilot wires follow the same path as the protected line.